Enhancement of Performance of TCP Using Normalised Throughput Gradient in Wireless Networks

Abstract

Transmission control protocol (TCP) is a dominant transport layer protocol for reliable data delivery in the internet. When packet loss occurs, TCP makes an implicit assumption that all packet loss is due to congestion. This results in unnecessary degradation in the TCP performance while traversing over a wireless link. In this paper, to improve the performance of TCP, we use NTG loss-predictor to distinguish congestion loss from transmission loss. Based on the prediction of type of loss, an appropriate algorithm is invoked by using NTG loss-prediction parameter \u03b2. Frequency of congestion loss and wireless loss predictions are analysed. Performance of TCP is improved further by discussing stability analysis over the system. A time-delay control theory is used and by constructing Hermit matrix, analysis is made for asymptotic stability of the system. Explicit conditions are derived for Pmax (RED controller) and \u03b2 (NTG loss controller) in terms of wireless network parameters. Using the characteristic equation of the matrix, convergence of the queue length at the bottleneck router is discussed. Analysis of convergence of queue length to a given target value is analysed. This establishes stability in the router performance. An approximate solution of queue length is derived. Our results provide better solutions for global stability and convergence conditions of the system.